Currently, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, and the like are used as commercial secondary batteries. Among them, lithium secondary batteries have little to no memory effect in comparison with nickel-based secondary batteries, and thus lithium secondary batteries are gaining a lot of attention for their advantages of free charging or discharging, low self-discharging, and high energy density.
A lithium secondary battery generally uses lithium oxide and carbonaceous material as a positive electrode active material and negative electrode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and an negative electrode plate respectively coated with the positive electrode active material and the negative electrode active material are disposed with a separator being interposed between them, and an exterior, namely a battery case, which seals and accommodates the electrode assembly together with an electrolyte.
Generally, a lithium secondary battery may be classified into a can type secondary battery where the electrode assembly is included in a metal can and a pouch type battery where the electrode assembly is included in a pouch of an aluminum laminate sheet, depending on the shape of the exterior.
Recently, secondary batteries are widely used not only for small-sized devices such as cellular phones but also middle-sized or large-sized devices such as vehicles and power storages. When being used for middle-sized or large-sized devices, a great number of secondary batteries are electrically connected to enhance capacity and output. In particular, in middle-sized or large-sized devices, pouch-type secondary batteries are frequently used since they are easily stacked and have light weight.
However, a pouch-type secondary battery does not have great mechanical rigidity and not easily maintains its stacked state since it is generally packaged with a battery case made of a laminate sheet of aluminum and polymer. Therefore, when configuring a battery module including a plurality of pouch-type secondary batteries, a cartridge is frequently used to protect the secondary batteries from external impacts or the like, prevent fluctuation of the secondary batteries and facilitate easier stacking of the secondary batteries.
A cartridge generally has a tetragonal plate shape with a hollow center, and at this time, its four side portions are configured to surround peripheral edges of a pouch-type secondary battery. In addition, a plurality of cartridges may be stacked to configure a battery module, and a secondary battery may be located in a vacuum space formed among the stacked cartridges.
However, if a battery module is composed using such cartridges or the like, a coupling component for fixing the cartridges is required. In other words, when a battery module is configured using a plurality of secondary batteries and a plurality of cartridges, coupling components for fixing them to each other, such as bolts, belts or screws, should be provided. In addition, in this case, the cartridge should have a configuration for the coupling with the coupling component, for example a hole or the like. In addition, in case of an existing battery module, end plates are provided at both outermost ends thereof in a stacking direction of the cartridges to ensure rigidity enough to fasten the coupling component.
However, such an existing battery module requires many coupling components, which results in complicated processes and structure and also bad price competitiveness. In addition, the battery module may not include many coupling components due to its limited space or processes, and when a vibration or impact occurs in such a configuration, the stress may be focused to the coupling component, which may cause the coupling component or a portion coupled thereto to be easily damaged. In addition, since such an existing battery module has great volume and weight due to coupling components and relevant configurations, it may be not easy to design a battery module with a small size and a light weight.